/*
 * $Id: PDFOutput.java,v 1.1.1.1 2001/10/29 19:51:08 ezb Exp $
 *
 * $Date: 2001/10/29 19:51:08 $
 *
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 * 
 */
package gnu.jpdf;

import java.io.*;
import java.util.*;

/**
 * This class is used to write a PDF document. It acts as a wrapper
 * to a real OutputStream, but is necessary for certain internal PDF
 * structures to be built correctly.
 *
 * @author Peter T. Mount
 * @author Eric Z. Beard, ericzbeard@hotmail.com
 * @author $Author: ezb $
 * @version $Revision: 1.1.1.1 $, $Date: 2001/10/29 19:51:08 $
 */
public class PDFOutput
{
	/**
	 * This is the actual OutputStream used to write to.
	 */
	protected OutputStream os;

	/**
	 * This is the OutputStream used to write each object to.
	 *
	 * <p>We use a separate stream, because we need to keep track of how
	 * many bytes have been written for each object for the xref table to
	 * work correctly.
	 */
	protected ByteArrayOutputStream baos;

	/**
	 * This is the current position within the stream
	 */
	protected int offset;

	/**
	 * This vector contains offsets of each object
	 */
	protected Vector<PDFXref> offsets;

	/**
	 * This is used to track the /Root object (catalog)
	 */
	protected PDFObject rootID;

	/**
	 * This is used to track the /Info object (info)
	 */
	protected PDFObject infoID;

	/**
	 * This creates a PDF OutputStream
	 *
	 * @param os The output stream to write the PDF file to.
	 */
	public PDFOutput(OutputStream os) throws IOException
	{
		this.os = os;
		offset = 0;
		offsets = new Vector<PDFXref>();
		baos = new ByteArrayOutputStream();

		// Now write the PDF header
		//
		// Note: As the encoding is fixed here, we use getBytes().
		//
		baos.write("%PDF-1.2\n".getBytes());

		// This second comment is advised in the PDF Reference manual
		// page 61
		baos.write("%\342\343\317\323\n".getBytes());
		offset = baos.size();
		baos.writeTo(os);
	}

	/**
	 * This method writes a PDFObject to the stream.
	 *
	 * @param ob PDFObject Obeject to write
	 * @exception IOException on error
	 */
	protected void write(PDFObject ob) throws IOException
	{
		// Check the object to see if it's one that is needed in the trailer
		// object
		if(ob instanceof PDFCatalog)   rootID=ob;
		if(ob instanceof PDFInfo)              infoID=ob;

		offsets.addElement(new PDFXref(ob.getSerialID(),offset));
		baos.reset();
		ob.write(baos);
		offset+=baos.size();
		baos.writeTo(os);
	}

	/**
	 * This closes the Stream, writing the xref table
	 */
	protected void close() throws IOException
	{
		// Make sure everything is written
		os.flush();

		// we use baos to speed things up a little.
		// Also, offset is preserved, and marks the begining of this block.
		// This is required by PDF at the end of the PDF file.
		baos.reset();
		baos.write("xref\n".getBytes());

		// Now a single subsection for object 0
		//baos.write("0 1\n0000000000 65535 f \n".getBytes());

		// Now scan through the offsets list. The should be in sequence,
		// but just in case:
		int firstid = 0;                    // First id in block
		int lastid = -1;                    // The last id used
		Vector<PDFXref> block = new Vector<PDFXref>();        // xrefs in this block

		// We need block 0 to exist
		block.addElement(new PDFXref(0,0,65535));

		for(Enumeration en = offsets.elements(); en.hasMoreElements(); ) 
		{
			PDFXref x = (PDFXref)en.nextElement();

			if(firstid==-1) 
				firstid=x.id;

			// check to see if block is in range (-1 means empty)
			if(lastid>-1 && x.id != (lastid+1))
			{
				// no, so write this block, and reset
				writeblock(firstid,block);
				block.removeAllElements();
				firstid=-1;
			}

			// now add to block
			block.addElement(x);
			lastid = x.id;
		}

		// now write the last block
		if(firstid>-1)
			writeblock(firstid,block);

		// now the trailer object
		baos.write("trailer\n<<\n".getBytes());

		// the number of entries (REQUIRED)
		baos.write("/Size ".getBytes());
		baos.write(Integer.toString(offsets.size()+1).getBytes());
		baos.write("\n".getBytes());

		// the /Root catalog indirect reference (REQUIRED)
		if(rootID != null) 
		{
			baos.write("/Root ".getBytes());
			baos.write(rootID.toString().getBytes());
			baos.write("\n".getBytes());
		}
		else
			throw new IOException("Root object is not present in document");

		// the /Info reference (OPTIONAL)
		if(infoID != null) 
		{
			baos.write("/Info ".getBytes());
			baos.write(infoID.toString().getBytes());
			baos.write("\n".getBytes());
		}

		// end the trailer object
		baos.write(">>\nstartxref\n".getBytes());
		baos.write(Integer.toString(offset).getBytes());
		baos.write("\n%%EOF\n".getBytes());

		// now flush the stream
		baos.writeTo(os);
		os.flush();
	}

	/**
	 * Writes a block of references to the PDF file
	 * @param firstid ID of the first reference in this block
	 * @param block Vector containing the references in this block
	 * @exception IOException on write error
	 */
	protected void writeblock(int firstid,Vector block) throws IOException
	{
		baos.write(Integer.toString(firstid).getBytes());
		baos.write(" ".getBytes());
		baos.write(Integer.toString(block.size()).getBytes());
		baos.write("\n".getBytes());
		//baos.write("\n0000000000 65535 f\n".getBytes());

		for(Enumeration en=block.elements(); en.hasMoreElements(); ) 
		{
			baos.write(en.nextElement().toString().getBytes());
			baos.write("\n".getBytes());
		}
	}
} // end class PDFOutput